The following problems will be investigated by digestion studies and physical investigation and hybridization studies of products. 1. Do the "phased" regions of chromatin correspond largely to the "tight" oligomers recently discovered? Are these especially populous in yeast nuclei? Do they correspond to transcribed regions, or are they randomly distributed? 2. At what point in the fertilization or early development of spisula embryos does chromatin reorganization occur? 3. Do histone cores pack cooperatively or non-cooperatively in reconstitution of chromatin oligomers? What is the role of H1? 4. Are there any detectable changes in overall chromatin structure during the cell cycle of HeLa?